In the late 1990s, the automotive industry had great expectations for gasoline (petrol) direct injection (GDI). The technology was heralded as the panacea for fuel economy and emissions, with a potential 20% improvement in both compared to conventional gasoline engines. At the time, manufacturers predicted that GDI engines would represent 25% of the total European engine market by 2003. But where are the results today? Well, it is certainly true that volumes of GDI vehicles on the road today fall well short of the predictions made four or five years ago.
“The original promises put forward for the first generation GDI systems were certainly overstated,” said Ed Martin, product line manager of Delphi Corp’s gasoline direction systems. “The fuel economy benefits that were touted at the time were largely based on a stop-go driving mode in Japan. However, in Europe and more so in the US, a lot of the driving situations don’t really lend themselves to getting this type of performance out of GDI. Also, there were some technical shortcomings from the first generation systems that, in addition to the fuel economy, did not really come through.”
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So does GDI run the risk of being a disappointment? “In my opinion, the disappointment is probably limited to the fuel system suppliers and car manufacturers, not the consumers,” said Terry Stinson, vice president and general manager of Siemens VDO’s powertrain gasoline systems and fuel components business. “With any new technology there is a learning curve and we are in the steep part of that curve. Disappointment soon fades when there are obvious advantages to be exploited.”
In Europe, the sluggish take-up of GDI could change in the second half of this decade, as VW remains committed to going 100% direct injection with its gasoline fleet by 2005.
Terry Stinson also reckons that the biggest benefit of GDI, fuel economy, is less of an issue for Americans. He said: “Fuel is inexpensive [in the US] compared to Europe and this fact translates into America’s push for larger, more powerful, less fuel-efficient vehicles. Another contributor is that between the fuels and after-treatment systems available, the predicted fuel savings in a real world application weren’t delivered with stratified charge systems. I am referring to the use of NOx storage cats. Also, the cost and complexity of the stratified systems doesn’t justify the actual fuel savings. The payback in fuel economy in the US would not justify the added cost to the vehicle, especially if this cost translated a commensurate incremental additional price increase to the vehicle. Today’s combustion systems and fuel systems also do not fully exploit the fuel economy benefits available from stratified combustion. The next generation of GDI technologies in Europe will offer these benefits. In the US, conventional low-pressure injection will be the standard for the next five years and likely beyond.”
Manufacturers believe that the current downsizing trend and the use of boosted engines in Europe will also increase the demand for direct injection. “There are distinct advantages of boosting a stratified direct injection engine in terms of drivability (higher exhaust flows) and fuel economy,” said Terry Stinson. “Due to fast actuators like our Piezo injector, combustion systems of the future will have a much broader stratified operating range, further increasing their fuel economy potential. As after-treatment systems evolve and fuels improve due to legislation, GDI will become a more attractive alternative. I predict that this will start as a European and possibly Asian trend and come to North America when fuel price increases warrant the attention and justify the added costs,” he added.
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By GlobalDataAlthough refineries have promised to reduce the sulphur content, the gasoline that is currently supplied (which has a high proportion of sulphur) will continue to cancel out any fuel savings gained from using GDI technology. It is more of a political question than a technical one. It is clear, however, that it is technically feasible to reduce sulphur content. We only need to look at Japan where they have already adopted legislation for very low sulphur content in their fuels. It can be done. The question is: at what expense and how quickly?
It is also clear that all manufacturers are working toward using spray-guided systems, typically with the injector mounted in the cylinder head. That requires significant base engine changes, requiring big decisions from the vehicle makers. Everyone is looking to ensure that the technology is truly viable in order that they can justify putting the capital expenditure in place.
Europeans fuel demand for diesel
The popularity of diesel-powered cars has led to a significant shift in the European car parc. The improvement in diesel engine design has significantly reduced exhaust emission while enhancing vehicle performance capabilities. Vehicles equipped with diesel engines now account for 4.9 million units in Europe, or a record high of 33% of the market. By 2006, it is predicted the number may top 7.3 million units, or 47%.
In terms of new diesel market share, Austria, Belgium, Spain and Luxembourg are the largest markets in Western Europe, with more than half their new car sales taken by diesel models. Both France and Germany register over one million units, closely followed by Italy with over 800,000 units.
Overall across Europe, high fuel prices are driving this trend toward diesel-powered cars. Moreover, carmakers are counting on diesels to reduce carbon dioxide emissions, a major contributor to global warming. European Union environment ministers aim to reduce average carbon dioxide emissions to 140 grams per kilometre by 2008. Regulators want a further reduction to 120 grams by 2010. Most new cars (gasoline and diesel) currently exceed 180 grams. About 95% of diesel engines are turbocharged. “When Euro IV goes into effect in 2005, internal combustion measures alone will no longer be sufficient for very heavy vehicles,” said Dr Ulrich Dohle, executive vice president of Bosch‘s diesel systems division. “An efficient exhaust after-treatment with particulate filter and an additional DeNOx catalyst will become necessary for some vehicles. A similar development will occur for commercial vehicles.”
Direct injection and common rail technology, which injects fuel directly into the combustion chamber at ultra high pressure with electronic control, have boosted diesel’s performance, and common rail technology has transformed the diesel engine’s noisy and dirty image. Volkswagen, PSA Peugeot-Citroën and Renault are considered leaders in this technology. Renault was one of the first to bring the benefits of direct injection to mass-market diesel engines in 1998 and now it has further refined the technology and is offering dCi or ‘direct common rail injection’ engines. The ‘rail’ contains fuel at very high pressure and exact amounts of it are fed to the cylinders under the control of the engine’s sophisticated control system. The system also provides a pre-injection of fuel just before the main fuel injection, optimising the rate at which pressure rises in the cylinder and lowering thermal load at the point of combustion. This makes for a quieter engine. In addition, the injection system is self-regulating, so that any wear in the engine is compensated for. The dCi engines are thus quieter, more powerful and more economical than their predecessors were.
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But will it catch on in North America?
For some time, American drivers have seen diesels as noisy, smelly and dirty engines. But according to J.D. Power and Associates, diesels will make a big comeback in the US in the second half of this decade. In North America, diesel engines are used primarily by the commercial trucking industry and in full-sized, heavy-duty pickups. But advances in diesel technologies, such as the common rail injection systems that make a diesel engine run quieter, reduce emissions and improve fuel economy, will help US consumers accept diesels in pickup trucks and cars.
Since 1999 J.D. Power has noted an increasing interest by US consumers in fuel-efficient vehicles. Their observations are backed up by public opinion survey of 1,000 consumers, commissioned by the Diesel Technology Forum, which found that more than half have a positive view of diesel power, including diesel in the automotive industry. In fact, a report from the US Diesel Technology Forum contrasts the different approaches to diesel-powered light cars and trucks in Europe and the US and suggests that the US could benefit by copying the European approach. Diesel car sales now account for around 33% in Europe and the technology is becoming increasingly popular in luxury cars. In the US however, light-duty diesels make up less than 1% of all cars sold. Government emissions and fuel tax policies have encouraged this growth in Europe, says the report, while in the US, government initiatives have hindered its growth, especially by emphasising control of NOx (nitrous oxide) and particulate matter from exhausts instead of the greenhouse gases. The report notes that diesel engine fuel efficiency can be improved by 40% – 60% over gasoline engines, while the latest direct injection diesels can better that by a further 20% – 40%.
In the US, Bosch points out that an increasing number of sports-utility vehicles, vans and pickups are being fitted with Bosch high-pressure direct injection systems. Bosch reports growing interest in the US in engines which are low in fuel consumption and toxic emissions but high in torque. In 2000, Bosch began supplying common rail injection systems to the Duramax engines of GMC’s Sierra and Chevrolet’s Silverado pickup trucks. Bosch also supplies common rail systems for Chrysler’s Dodge Ram 2500/3500 pickups. Bosch’s Automotive Diesel Technology Centre in Farmington Hills, Michigan is responsible for adapting common rail systems for the local market. The common rails are made at the company’s 17,000-m² facility in Charleston, South Carolina. Bosch has invested some $160 million in this plant and expects direct injection diesel engines to have gained a ‘significant’ market share by 2010.
